The present invention relates generally to an electronic clinical sphygmomanometer and, more particularly, to an electronic clinical sphygmomanometer for measuring blood pressure on the basis of a Korotkoff-sound signal in a pulse-wave gate signal.
In general, conventional clinical sphygmomanometers of this type are susceptible to external noise derived from such factors as motion of the body since Korotkoff-sound signals are weak, thus occasionally resulting in erroneous measurements. To eliminate such erroneous measurements, Japanese Patent Application No. 279225/1986 proposes an electronic clinical sphygmomanometer of the type which is arranged to utilize the correlation between a pulse-wave signal and a Korotkoff-sound signal to compare the level of the pulse-wave signal with a predetermined level, thereby creating a pulse-wave gate signal for the purpose of improving noise resistance.
However, the wave forms of pulse-wave signals are not constant and, in addition, the correlation between pulse-wave signals and Korotkoff-sound signals is not constant. As a result, a Korotkoff-sound signal occasionally deviates from a pulse-wave gate, and it has therefore been difficult to reliably detect Korotkoff-sound signals.